An announcement from the Arkansas State Racing Commission in early March that it would begin randomly testing Oaklawn Park runners for elevated TCO2 was widely lauded as another step toward improved integrity in the state. The commission adopted a TCO2 threshold in February which brought its rules for allowable levels in line with national standards. Along with out-of-competition testing and broader post-race drug tests, this was the latest in a series of moves designed to improve welfare and safety in Arkansas racing.
The decision did make us wonder – wasn't TCO2 something the industry dealt with a long time ago? Kentucky and Louisiana became the last states to outlaw manipulation of TCO2 levels in the 1990s and California started testing for elevated levels in 2004. Although regulators say TCO2 overages aren't ubiquitous, regulations (and drug testing contracts) regarding its detection vary between states.
What is TCO2, again?
It's important to understand TCO2, or total carbon dioxide, is present in horses naturally as a result of normal metabolic processes. TCO2 varies in a horse's blood as it increases or decreases in balance with electrolytes like sodium, potassium, and chloride, as well as protein and lactate. Sodium and potassium sit on one side of the equation, with TCO2, protein, lactate, and chloride on the other; if something makes one part of the equation go up, an element on the other side of the equation must go down to balance it out.
TCO2 may increase or decrease in response to electrolyte or protein changes from certain feeds, as well as exercise (which increases lactate as the muscles are used, thereby reducing TCO2). When someone tries to manipulate TCO2, they're hoping to increase TCO2 levels and decrease lactate levels. Lactate is the byproduct of aerobic exercise and causes muscles to feel tired.
A study published in the Equine Veterinary Journal in 2006 showed a number of other factors associated with TCO2 levels, including gender (male horses tended to have higher TCO2 levels), class of race (maidens tended to have lower TCO2), finish position (horses hitting the board had higher TCO2 than those that did not), and oddly, cloudy weather. It's unclear what caused these differences, and whether TCO2 levels explained a horse's performance (with a better performance being a result of higher TCO2) or if TCO2 readings were more a marker of a given horse's fitness.
The study also found trainer- and horse-specific trends, which doesn't necessarily suggest trainers in the study were intentionally manipulating TCO2 levels. It's possible different barns might create different environments for TCO2 readings given their combination of feed and exercise programs.
One thing that probably doesn't impact TCO2: electrolyte pastes and supplements. Commercially-available electrolyte supplements contain all three minerals (sodium, potassium, and chloride) involved in the TCO2 equation, thereby preventing an imbalance.
Milkshaking, one method of trying to artificially manipulate TCO2, involves delivering a dose of sodium ions along with bicarbonate, commonly from an ingredient like baking soda. This is intended to elevate TCO2 and therefore reduce lactate as the horse's body works to keep everything in balance. Milkshaking is thought to have crossed into Thoroughbred racing from the Standardbred world in the late 1980s. The practice gets its name from the slurry consistency of the paste delivered directly to the horse's stomach via a nasogastric tube. Some trainers evolved the practice to include “bullets” of a similar paste-like mix, given with a dosing gun to the back of the throat.
The problem with both these delivery methods, said HFL Sport Science Laboratory Director Dr. Richard Sams, is they may not get enough baking soda in most horses to have an impact. Baking soda doesn't dissolve easily, which is why the slurry is so thick, so only a portion of it could be absorbed to adjust the bicarbonate level in the blood. That's if the trainer inserts the nasogastric tube correctly and doesn't accidentally pump the slurry into the horse's lungs instead (which Sams said has happened). Even once it gets there, Sams isn't sure a milkshake necessarily has the impact trainers might hope.
“Because the bicarbonate [in the horse's blood] is a physiological response to different factors, I don't see how it can directly influence other factors,” said Sams. “For example, it is not going to be able to suppress the formation of lactate ion from lactic acid. The lactic acid is a byproduct of anaerobic metabolism of glucose. That's what happens during the race.”
Racing Medication and Testing Consortium Executive Director and COO Dr. Dionne Benson has quizzed trainers and regulators who were around in the days of frequent milkshaking and learned the practice seemed to be hit and miss, depending upon the individual.
“From what I understand from talking to people, just like everything, it doesn't work on every horse,” said Benson. “There are some horses who had great benefit and some horses who didn't improve at all. Without knowing what people did, I'm guessing what happened is they tried different things on different horses and see what improved that individual. And I'm sure you had people who did it to every horse, because if it worked on one, it might work on all of them.”
Furosemide (Lasix) also impacts TCO2, since it dehydrates horses and reduces chloride, which prompts an increase of TCO2 to compensate. For this reason, horses running with furosemide are expected to have slightly elevated TCO2 compared to those not receiving the drug. If a horse's TCO2 is elevated, Sams said he can tell whether furosemide is to blame based on the chloride levels. Unusual electrolyte levels along with high TCO2 could also indicate a horse is ill or suffering from a chronic condition.
The testing process for TCO2 requires fairly rapid action, as it can only be measured accurately in blood for a limited time after collection. Proper storage of the blood sample is also important because electrolytes inside red blood cells can shift if the sample is not spun properly (a fact which was the basis for trainer Karl Broberg's fight against two TCO2 overages in 2013), creating an erroneous reading.
State by state
Unsurprisingly, thresholds for TCO2 vary across states. The international standard is 36 millimoles per liter, while the recommended United States threshold is 37 mmol/L. That figure was already supposed to take into account the needed flexibility for horses running on furosemide, but a few states – Arkansas, West Virginia, and New York – have rules allowing an extra two mmol/L for horses running with furosemide.
According to the website Horse Racing Reform, eight states including Florida, Maryland, and Oklahoma, do not have published rules quantifying the threshold for TCO2. As with post-race drug testing, there may also be a discrepancy between published rules and testing procedures. Florida's current drug testing contract does not address TCO2 specifically. Louisiana's contract specifies only that blood samples “may also be used to investigate the presence of alkalinizing agents,” which leaves the door open for the lab to start or stop testing for it at any time.
In states where testing is taking place, TCO2 samples are obtained similarly to cobalt or out-of-competition samples in that tests are conducted on a relatively small portion of the population at random. At Kentucky racetracks, one or two races are chosen randomly and the entire field is tested to prevent any perceived disadvantage to individual runners from being pulled aside and upset prior to the race. Similar policies are in place in other states requiring random testing of all horses in one or two races per day.
International testing for TCO2 varies widely. Ireland only recently began testing for the substance. Testing is not performed at all in Japan, where horses are under surveillance sufficiently officials feel they are not likely to be milkshaked. Random sampling takes place in several international jurisdictions, and in Singapore, every horse is sampled before every race (though no TCO2 overages have been found in 11 years).
The penalties for a TCO2 positive in the United States can be stiff if the trainer and owner involved are repeat offenders of medication rules. In Kentucky, if a horse tests positive for elevated TCO2 and the trainer already has one other positive drug test in the past 365 days, suspensions can run 90 to 180 days. A total of four or more total testing offenses in a year, and the trainer may get a year suspension or a ban. California has a similar program graduating penalties as a trainer is found guilty of multiple TCO2 violations.
Association of Racing Commissioners International model rules support a Class B penalty for TCO2 excesses, which results in disqualification and purse loss for owners and a minimum 15-day suspension and $500 fine for trainers on their first offense.
A handful of states have adopted the entire drug overage penalty schedule laid out by the ARCI, though states not adopting the schedule may have similar rules specific to TCO2.
“We don't have very many of these [in Kentucky],” said Sams. “I think the trainers have made the decision it just isn't worth it. The benefit doesn't outweigh the risk. I think maybe more importantly, I think trainers here realize that others aren't gaining an advantage by using bicarbonate. That's probably the greatest disincentive.”
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